Smallpox conundrum

Smallpox is one of the deadliest viruses in our history. It killed more than 300 million people in the 20th century alone.

More than 30 years ago, the World Health Organization declared smallpox eradicated.

The triumphant announcement came after a global vaccination campaign, and painstaking efforts were made to ensure every last sample of smallpox - known as the variola virus - was destroyed.

Just a few specimens were preserved. They are currently stored in liquid nitrogen in two high-security laboratories in Russia and the United States.

Later this month the WHO's decision making body, the World Health Assembly (WHA), meets to decide on when to destroy these last variola stocks.

But some scientists say it is less a question of when the stocks should be destroyed, and more a question of whether they should be destroyed at all.

To kill or not to kill?

The samples were set aside so that scientists could conduct WHO-approved "essential public health" research into the virus - specifically, to develop a new vaccine, antiviral drugs and better diagnostic techniques.

This isn't the first time the WHA has considered incinerating the stocks. The issue was most recently on the agenda in 2011, but no decision was made.

However, there have been significant steps forward in smallpox recent research. And as a result, in 2013, a WHO-appointed group of scientists said it could no longer justify keeping live variola virus samples.

But not everyone agrees.

"On this point there are some differences between member states," says Dr Alejandro Costa, head of the emergency vaccination and stockpiles team with the WHO's smallpox program.

"Countries in favor of the destruction argue the disease doesn't exist anymore, and we already have one vaccine, and we are soon to have another antiviral, so there is no need to keep the virus."

Unfinished business

But others warn against destroying every last trace of variola.

Dr Inger Damon is the director of the WHO Collaborating Center for Smallpox at the Center for Disease Control in Atlanta, Georgia, where one of the remaining live samples is stored.

In an opinion piece published this May in the science journal "PLoS Pathogens," Dr Damon argues there are still "significant gaps" in what we know about smallpox.

"We've been working on a smallpox research agenda for 10 years, and we've made considerable progress in terms of advanced development of less reactogenic vaccines as well as antivirals," she told DW. "But we feel that we're not finished with what we originally set out to do, and that continuing to be able to access the virus for testing is going to be important for the near term."

Bioterrorism fears

There are concerns that without more research, the international community would be unable to respond to a future threat, such as a bioterrorism attack.

Such concerns have grown since a 2001 anthrax attack in the US. The attack prompted the government there to bolster its smallpox vaccine stockpile.

There has also been speculation about the possibility of secret smallpox samples falling into the "wrong hands."

During the 1970s, the Soviet Union began to produce quantities of "weaponized smallpox."

Although these stocks are said to have been destroyed by the early 1990s, some experts believe smallpox vials may have been traded or stolen at the time the Soviet Union broke up.

A vulnerable population?

There is also the issue of public health and prevention.

Routine smallpox vaccination was stopped decades ago, so entire populations would be susceptible if the virus re-emerged, says Dr William Schaffner, an infectious diseases specialist and professor of preventive medicine at the Vanderbilt Medical Center in Nashville, Tennessee.

He wants to see the live virus samples destroyed as soon as possible.

"We must remember that the smallpox virus caused among the greatest plagues that [we] have ever seen," says Dr Schaffner. "It was an enormous triumph of public health when we rid the world of smallpox."

Building a live virus from scratch

Smallpox is part of the orthopoxvirus family and is believed to have emerged in humans around 10,000 BC.

Although it's been eradicated, advances in modern science mean it's technically possible to recreate the virus from scratch - but this is prohibited under WHO regulations.

"Molecular biology has advanced in leaps and bounds, and I think the case for keeping the live virus is weakening because of that," says John McConnell, editor of "The Lancet Infectious Diseases" journal. "Providing you have a comprehensive library of genetic sequences, technology should be in a position where you can reconstruct the virus from that material."

Still, says McConnell, there could be a future scenario in which it would be handy to have the live variola virus in stock. For example, if a pox virus occurring in the wild mutated into a strain that caused human disease.

"The history of infectious diseases has taught us to expect the unexpected…and something might happen for which just the availability of the genetic sequence isn't sufficient," says McConnell.

Dr Inger Damon believes keeping the variola samples - and research - alive could also help combat lesser known bugs.

"The work that's being done to develop less reactogenic vaccines and diagnostic approaches will certainly be useful for identification and preparedness for these other emerging orthopox viruses," says Damon.

The World Health Assembly meets to decide on when to destroy the live variola samples in Geneva on May 19-24.